The water purification system in the related art employs PP (polypropylene) cotton for a pre-filter cartridge and a series RO (reverse osmosis) filter cartridge, and purifies water via a multistage filter cartridge. The whole water purification system has disadvantages of complex pipeline connection, inconvenient installation and replacement, many joints and leakage risk points. Moreover, the service life of each filter cartridges in the multistage filter cartridge is not consistent, such that the user may have to change three to five filters. Frequent purchasing and replacement by professionals will degrade user experience and increase the cost of use.